322 



RADIATION BIOLOGY 



0.5 1 2 5 10 20 50 100 200 



LINEAR ENERGY TRANSFER, kev/// 



Fig. 6-2. Variation of biological effectiveness with linear energy transfer (LET). 

 Further data in Table 6-1 as follows: Stichococcus, item 25; fern spore, item 30; bean 

 root (lethal action), item 80; bean root (mitosis), item 81. 



Although complete coverage of the literature has not been attempted, 

 an effort has been made to include in Table 6-1 a fair sampling of the 

 available experiments in which a clear influence of LET was observed. 

 Also included in Table 6-1 are investigations in which LET was varied 

 as much as a factor of 5, regardless of the relative effectiveness observed. 

 A number of investigations which do not fall in either of these two cate- 

 gories are not tabulated but are distinguished by daggers in the bibliog- 

 raphy. Many papers were examined but not used, for one or both of the 

 following reasons: (1) Most papers appearing before the adoption of the 

 international roentgen in 1927 have been omitted because of uncertainty 

 concerning identical response of measuring devices to radiations of 

 different quality. (2) Many papers dealing with skin have been omitted 

 because of uncertainties involved in the determination of energy absorbed 

 in the tissues of interest or because of inadequate numbers of individuals 

 investigated. 



Explanatio7i of Table 6-1. Table 6-1 consists of eight columns. The 

 first contains item numbers, to be used for reference to the various experi- 

 ments. The second lists the various objects or systems which were 

 investigated. These are arranged in a roughly "taxonomic" order, as 

 follows: water and simple aqueous solutions; proteins and other colloids, 

 including enzymes; viruses, including bacteriophages; bacteria; yeast 

 cells; unicellular algae; higher fungi; ferns; worms (Ascaris); insects (Dro- 



